To participate in Prime Exclusive Discounts, your product must display a reference price that indicates to customers the value of your offer.
An example of a reference price is a “was” price or list price.
On regular days, the Prime Exclusive Discount must be 5% lower than the reference price.
During special events, such as Prime Day and Black Friday, Prime Exclusive Discounts must be 10% lower than the reference price.
To learn more, go to Amazon policy on reference prices.